Device for simultaneously detecting several spectral ranges of a light beam

ABSTRACT

An apparatus for simultaneous detection of a plurality of spectral regions of a light beam ( 1 ), in particular for detection of the light beam ( 1 ) of a laser scanner ( 2 ) in the detection beam path of a confocal microscope, is characterized, in order to achieve a simple configuration with small overall size and elimination of the defocusing effect, by an arrangement ( 3 ) for spectral spreading of the light beam ( 1 ) and an arrangement ( 4 ) for splitting the spread beam ( 5 ) out of the dispersion plane ( 6 ) into spectral regions ( 7, 8, 9 ), and for subsequent detection of the split spectral regions ( 7, 8, 9 ).

CROSS-REFERENCES TO RELATED APPLICATIONS

The present application is the U.S. national phase under 35 U.S.C. 371of International Application No. PCT/DE99/00210 filed Jan. 28, 1999claiming priority of German Patent Application No. 198 03 151.3 filedJan. 28, 1998.

FIELD OF THE INVENTION

The invention concerns an apparatus for simultaneous detection of aplurality of spectral regions of a light beam, in particular fordetection of the light beam of a laser scanner in the detection beampath of a confocal microscope.

BACKGROUND OF THE INVENTION

Apparatuses for simultaneous detection of a plurality of spectralregions of a light beam have been known from practical use for sometime, and are referred to as “multiband detectors.” These are complexoptical arrangements that use an additional optical system to allowmultiple focusing. Arrangements of this kind require a great deal ofspace for spectral multiband detection, and their resulting overall sizeis thus not inconsiderable. In addition, a defocusing effect oftenoccurs therein, so that additional refocusing with the additionaloptical system—with reference to the respective spectral region—isnecessary.

SUMMARY OF THE INVENTION

It is therefore the object of the invention to configure and develop anapparatus for simultaneous detection of multiple spectral regions of alight beam, in particular for detection of the light beam of a laserscanner in the detection beam path of a confocal microscope, in such away that a small overall size can be achieved with a simpleconfiguration, the intention being to avoid, to a very large extent, thedefocusing effect that occurs in the existing art.

The apparatus of the generic type according to the present inventionachieves the aforesaid object by way of an arrangement for spectralspreading of the light beam and an arrangement for splitting the spreadbeam out of the dispersion plane into spectral regions, and forsubsequent detection of the split spectral regions (slit/detectorarrangement).

According to the present invention, it has been recognized thatsimultaneous detection of a plurality of spectral regions of a lightbeam is readily possible if the light beam is first spectrally spreadout and if a splitting of the spread beam out of the dispersion plane isthen performed. Splitting of the spread beam out of the dispersion planeis accomplished, according to the present invention, by way of aparticular optical arrangement, the partial beams split into spectralregions, or the spectral regions themselves, being detectedsimultaneously. What is essential here is that the actual splitting intospectral regions is preceded by a spreading of the light beam, so thatthe splitting out of the dispersion plane can be performed on the spreadbeam. Multiple focusing with an additional optical system is in anyevent not necessary here.

As already set forth, according to the present invention two opticalarrangements are provided, namely one for spectral spreading of thelight beam and another for splitting and subsequent detection. Thearrangement for spectral spreading of the light beam can be preceded bya pinhole onto which the incoming light beam is focused; the pinhole canbe directly downstream from a laser scanner. What is essential in anycase is the focusing of the light beam onto the pinhole arranged in thebeam path.

From there, the divergent beam proceeds to the arrangement for spectralspreading of the light beam, this arrangement comprising focusingoptical systems and dispersion means. In the interest of particularlysimple design, the dispersion means can be embodied as a prism. Infurther advantageous fashion, a respective focusing optical system,which in turn can comprise a lens arrangement, is arranged before andafter the dispersion means or prism.

The divergent beam proceeding from the pinhole to the prism is focusedby the focusing optical systems into the slit/detector arrangement (tobe explained later), from whence the splitting into spectral regionstakes place.

Particularly in the interest of small overall size, reflection means forfolding back the spread beam are arranged after the arrangement forspreading the light beam; the reflection means can be a mirror-coatedsurface or a mirror. In any event, the fact that the spread beam isfolded back at least once allows a small overall size for the apparatusas a whole.

As already mentioned earlier, the light beam can be focused into theslit/detector arrangement by way of the focusing optical systems. Thisslit/detector arrangement is thus arranged in the beam path of thespread beam and comprises reflective surfaces, forming slit diaphragms,which break down the spread beam, on the one hand by slit formation andon the other hand by reflection out of the dispersion plane, into aplurality of partial beams and thus image the individual spectralregions onto the corresponding detectors. In other words, the slitdiaphragms provide partial transmission (corresponding to the slitwidth) of the beam arriving at them, and on the other hand providereflection at the reflective surfaces provided therein, so that evenwith one slit diaphragm and two reflective surfaces (one reflectivesurface on either side to form the slit diaphragm), a breakdown intothree partial beams and thus into three spectral regions is possible.This division is performed on the spread beam, out of its dispersionplane. Of course both the partial beam transmitted through the slitdiaphragm and the reflected partial beam can once again strike a slitdiaphragm and can be broken down there again as explained above. Thedivision into a plurality of partial beams is thus made possible by amultiple arrangement of slit diaphragms having corresponding reflectivesurfaces.

The split partial beams pass directly to detectors, the number ofdetectors corresponding to the number of partial beams.

It is furthermore essential for the slit diaphragms provided here thatthey be placed or arranged approximately at the focus of the spreadbeam. The reflective surfaces of the slit diaphragms are embodied asmirror-coated surfaces or mirrors; the mirror-coated surfaces can, forexample, be vacuum-evaporated in accordance with the support material.

With regard to a concrete embodiment of the slit diaphragms, it isadvantageous if the mirror-coated surface is associated with a slitdiaphragm jaw forming the slit diaphragm, and if the slit diaphragm jawis adjustable, or movable or displaceable, in terms of its positionwhich defines the slit diaphragm, the region of the spread beam to bereflected, and optionally the reflection angle. By adjusting the slitdiaphragm jaw it is thus possible to define not only the spectral regionof the transmitted partial beam and the reflected partial beam, but alsothe direction in which the reflected partial beams travel. Thearrangement of the detectors is thus variable at least within a certainrange.

Concretely, the slit diaphragm jaws could be embodied as respectivecubic or, for example, also quadrangular bars having an at leastpartially mirror-coated surface. One of the surfaces then serves, atleast partially, as a reflective surface, this being the surfaceadjacent to the actual slit. A solid glass element, which in accordancewith the type of glass used can already offer a total reflection at itssurface, is suitable for manufacture of the slit diaphragm jaw. Inaddition, glass is easy to process and has an extremely low coefficientof thermal expansion, so that temperature-related adjustment of thearrangement is not necessary.

In further advantageous fashion, the slit diaphragm jaws are embodied inthe manner of a slider with a rotationally driven spindle and with acorresponding thread. Adjustment of the slit diaphragm jaws can thus beaccomplished via actuators that cause an advance and optionally arotation of the mirror-coated surface of the slit diaphragm jaw.Displacement of the position of the slit diaphragm jaw allows the slitwidth and the width of the reflected beam, and thus of the respectivespectral region, to be adjusted. Adjustment of the angular position ofthe slit diaphragm jaw and thus the reflection angle makes possiblealignment with immovably positioned detectors. The actuators can be anydesired manual actuation systems. Electric motors, in particularelectric motors with a fine adjustment system, advantageously serve asactuators.

Within the slit/detector arrangement, features can be provided tosuppress flare, for example so-called beam traps or stops such as thosesufficiently known from the existing art for flare suppression.

Any conventional detectors, preferably photomultipliers, can be used asdetectors for the various spectral regions or colors. It is alsopossible, for example, to use commercially available CCD sensors.

In the interest of a compact design for the apparatus as a whole, it isadvantageous if the arrangement for spectral spreading of the light beamand the slit/detector arrangement are carried by a single chassis thatis mounted or can be fastened directly to the laser scanner. Theslit/detector arrangement with the slit diaphragm jaws provided thereoncould be arranged in a housing that can be handled as an insert. Theinsert could in turn be adjustable in terms of its position, in order toestablish the incidence angle and the dispersion plane of the spreadbeam.

Lastly, it is also conceivable for the housing for the slit/detectorarrangement to be largely thermally insulated, specifically in ordereffectively to eliminate thermal influences on the arrangement therein.

BRIEF DESCRIPTION OF THE DRAWINGS

There are various ways of advantageously embodying and developing theteaching of the present invention. Reference is made, for that purpose,to the explanation below of an exemplary embodiment of the inventionwith reference to the drawings. In conjunction with the explanation ofthe preferred exemplary embodiment of the invention, a generalexplanation is also given of preferred embodiments and developments ofthe teaching. In the drawings:

FIG. 1 shows, in a schematic depiction, an exemplary embodiment of anapparatus according to the present invention for simultaneous detectionof a plurality of spectral regions of a light beam, the slit/detectorarrangement being depicted therein as a “black box”;

FIG. 2 shows, in a schematic basic depiction, the manner of operation ofthe slit/detector arrangement; and

FIG. 3 shows, in a schematic depiction, one possible basic arrangementof the components of the slit/detector arrangement.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows, in a schematic depiction, an exemplary embodiment of anapparatus for simultaneous detection of a plurality of spectral regionsof a light beam 1, being in this case an apparatus for detection oflight beam 1 of a laser scanner 2 (indicated only schematically) in thedetection beam path of a confocal microscope (not shown in the Figure).

According to the present invention, the apparatus comprises anarrangement 3 for spectral spreading of light beam 1, and anarrangement, consistently referred to hereinafter as slit/detectorarrangement 4, for splitting spread beam 5 out of dispersion plane 6into spectral regions 7, 8, 9 and for subsequent detection of the splitspectral regions 7, 8, 9 by way of detectors 12, 10, 11.

FIG. 1 indicates that arrangement 3 for spectral spreading of light beam1 is preceded by a pinhole 13 onto which the incoming light beam 1 isfocused. From there, divergent light beam 14 passes to a prism 15,focusing optical systems 16 being arranged before and after prism 15.There divergent light beam 14 is focused into slit/detector arrangement4; in order to fold back beam 17 that has been spread by prism 15, saidbeam first strikes a mirror 18 and from there passes into slit/detectorarrangement 4 with corresponding focusing.

A means for diffracting spread beam 5, for example a transparentdiffraction grating or a reflective diffraction grating, can be locatedin the detection beam path after arrangement 3 in place of or inaddition to reflection means 18. As a further alternative, a means forrefracting spread beam 5, for example a prism, can be located in thedetection beam path after arrangement 3 in place of or in addition toreflection means 18.

It is further evident from FIG. 1 that both arrangement 3 for spectralspreading of light beam 1 and slit/detector arrangement 4 are associatedwith a chassis 19; chassis 19 can be fastened directly to laser scanner2. This is made possible, in particular, by the compact design of theentire arrangement.

FIGS. 2 and 3 show on the one hand the basic manner of operation and onthe other hand the general arrangement of the respective componentswithin slit/detector arrangement 4.

In slit/detector arrangement 4, spread beam 17 or 5 is guided by slitdiaphragm jaws 23 and mirror-coated surfaces 21 into a plurality ofpartial beams or spectral regions 7, 8, 9, out of dispersion plane 6, todetectors 10, 11, 12. In the depiction selected in FIG. 2, dispersionplane 6 lies perpendicular to the plane of the drawing (its projectionis labeled with the reference character 5). In the depiction selected inFIG. 3, dispersion plane 6 lies in the plane of the drawing.

In the depictions in FIGS. 2 and 3, both detectors 10, 11, 12 andactuators 22, embodied as electric motors, are shown only schematically.The same is true of slit diaphragm jaws 23 forming slits 20A and Btogether with mirror-coated surfaces 21 that are provided directly onslit diaphragm jaws 23.

FIG. 2 furthermore shows an enlargement of a reflected spectral region9, the reflection taking place at the mirror-coated end face of a slitdiaphragm jaw 23.

FIG. 3 clearly shows that portions of spectrally spread beam 5 enteringslit/detector arrangement 4 are deflected at mirror-coated surfaces 21upward and downward to detectors 10, 11. A further partial beam orspectral region 7 passes through slit 20A and arrives at detector 12.

FIGS. 2 and 3 also show that multiple slit diaphragms can be used. Byway of example, a second slit diaphragm 20B is shown in the path ofreflected partial beam 8. Accordingly, an additional spectral region 26can be detected at detector 27.

Actuators 22 allow adjustment of slits 20A and 20B between slitdiaphragm jaws 23, thus making possible individual adjustment ofspectral regions 7, 8, 9 whose partial beams ultimately reach detectors12, 10, 11.

Because the incident spread beam 17 or 5 is split out of dispersionplane 6, it is possible to place slit diaphragm jaws 23 with sufficientaccuracy at the focus of spread beam 17 or 5.

Lastly, be it noted that for the sake of a simplified depiction, onlytwo of the total of four actuators 22 are depicted in FIG. 3.

PARTS LIST

1 Light beam (arriving from laser scanner)

2 Laser scanner

3 Arrangement for-spectral spreading of light beam 5

4 Slit/detector arrangement

5 Spread beam

6 Dispersion plane (of spread beam)

7 Spectral region

8 Spectral region

9 Spectral region

10 Detector

11 Detector

12 Detector

13 Pinhole

14 Divergent light beam (after pinhole)

15 Prism

16 Focusing optical systems

17 Spread beam (after prism)

18 Mirror (for folding)

19 Chassis

20 Slit

21 Mirror-coated surfaces (on slit diaphragm jaws)

22 Actuator

23 Slit diaphragm jaws

25 Housing

26 Spectral region

27 Detector

What is claimed is:
 1. An apparatus for simultaneous detection of aplurality of spectral regions of a light beam comprising: a confocalmicroscope; a laser scanner defining a detection beam path in saidconfocal microscope; means for spectrally spreading said light beam at adispersion plane; and, slit/detector means for splitting said spreadbeam out of said dispersion plane into a plurality of spectral regionsand detecting said plurality of spectral regions.
 2. The apparatusaccording to claim 1, further comprising a pinhole in said detectionbeam path before said means for spectrally spreading said light beam,wherein said light beam is focused onto said pinhole.
 3. The apparatusaccording to claim 1, wherein said means for spectrally spreading saidlight beam includes a plurality of focusing optical systems in saiddetection beam path and means for dispersion of said light beam.
 4. Theapparatus according to claim 3, wherein said dispersion means includes aprism.
 5. The apparatus according to claim 3, wherein said plurality offocusing optical systems includes a first focusing optical systemarranged before said dispersion means and a second focusing opticalsystem arranged after said dispersion means.
 6. The apparatus accordingto claim 5, wherein said first and second focusing optical systems eachcomprise lens arrangements.
 7. The apparatus according to claim 5,wherein said light beam is focused by said first and second focusingoptical systems into said slit/detector means.
 8. The apparatusaccording to claim 1, further comprising reflection means located aftersaid means for spectrally spreading said light beam for redirecting saidspread beam.
 9. The apparatus according to claim 8, wherein saidreflection means is a mirror.
 10. The apparatus according to claim 1,further comprising diffraction means located after said means forspectrally spreading said light beam for diffracting said spread beam.11. The apparatus according to claim 10, wherein said diffraction meansis a transparent grating.
 12. The apparatus according to claim 10,wherein said diffraction means is a reflective grating.
 13. Theapparatus according to claim 1, further comprising refraction meanslocated after said means for spectrally spreading said light beam forrefracting said spread beam.
 14. The apparatus according to claim 13,wherein said refraction means is a prism.
 15. The apparatus according toclaim 1, wherein said slit/detector means includes a plurality ofreflective surfaces spaced apart to define a slit diaphragmtherebetween, whereby said spread beam is broken down into a pluralityof partial beams by transmission through said slit diaphragm andreflection by said plurality of reflective surfaces out of saiddispersion plane.
 16. The apparatus according to claim 15, wherein saidslit/detector means includes a plurality of detectors each positioned toreceive a respective one of said plurality of partial beams.
 17. Theapparatus according to claim 15, wherein said slit diaphragm is placedapproximately at the focus of said spread beam.
 18. The apparatusaccording to claim 15, wherein said plurality of reflective surfaces isa plurality of mirror-coated surfaces.
 19. The apparatus according toclaim 18, wherein each of said plurality of mirror-coated surfaces isassociated with a slit diaphragm jaw for positioning said mirror-coatedsurface, whereby said spectral region defined by transmission of apartial beam through said slit diaphragm and spectral regions defined byreflection of partial beams from said plurality of mirror-coatedsurfaces are adjustable.
 20. The apparatus according to claim 19,wherein each said jaw enables tilting of said mirror-coated surfaceassociated therewith to control the direction of travel of a reflectedpartial beam from said mirror-coated surface associated with said jaw.21. The apparatus according to claim 19, wherein each said jaw is aquadrangular bar having an at least partially mirror-coated surfaceforming said mirror-coated surface.
 22. The apparatus according to claim21, wherein each said jaw is a cube having an at least partiallymirror-coated surface forming said mirror-coated surface.
 23. Theapparatus according to claim 21, wherein each said jaw is fabricatedfrom glass.
 24. The apparatus according to claim 19, wherein each saidjaw is connected by thread to a rotationally driven spindle forpositioning said mirror-coated surface associated with said jaw.
 25. Theapparatus according to claim 20, wherein each said jaw is connected toan actuator for positioning and tilting said mirror-coated surfaceassociated with said jaw.
 26. The apparatus according to claim 25,wherein each said actuator is an electric motor.
 27. The apparatusaccording to claim 1, wherein said slit/detector means includes aplurality of detectors for detecting said plurality of spectral regions.28. The apparatus according to claim 27, wherein each of said pluralityof detectors is a CCD sensor.
 29. The apparatus according to claim 1,further comprising a chassis for carrying said means for spectrallyspreading said light beam and said slit/detector means, wherein saidchassis is connected directly to said laser scanner.
 30. The apparatusaccording to claim 29, further comprising a housing for carrying saidslit/detector means, wherein said housing is inserted into said chassis.31. The apparatus according to claim 30, wherein said housing isadjustable relative to said chassis to establish an angle of incidenceand said dispersion plane of said spread beam.
 32. The apparatusaccording to claim 30, wherein said housing is thermally insulated.